The XM Satellite Radio Software Module of an Embedded Car Audio System

JOURNAL OF SOFTWARE, VOL. 7, NO. 9, SEPTEMBER 2012 1981 The XM Satellite Radio Software Module of an Embedded Car Audio System Di Wu Dalian University of Technology, Dalian, China Email: [email protected] Chenxi Hou Dalian University of Technology, Dalian, China Email: [email protected] Limin Sun Institute of Information Engineering, Chinese Academy of Sciences, Beijing, China Email: [email protected] Yan Ling Dalian University of Technology, Dalian, China Email: [email protected] Jiangchuan Liu Simon Fraser University, Vancouver, Canada Email: [email protected] Abstract—XM radio service is an emerging satellite digital product design and manufacturing industry, digital car audio radio service suitable for automotive environment, it audio system [1] products are gradually getting into the offers users high-quality radio programs with better signal vision of more and more automobile users. The digital car coverage by adopting communication satellite broadcasting audio system products meet the visual and auditory technology. In order to incorporate XM radio function into entertainment demand of consumers for during a car ride, a digital car audio system based on the embedded system industry standard ITRON, we analyze both software and they offer brand new entertainment experience options hardware requirements of the XM function module in this for car passengers and drivers on the trip, and have work. Architectural design that separates the XM radio transformed itself into an indispensable composing part function module into five layers is given. The operating of on-board digital systems. In recent years, car system selected for the microcontroller used in the car audio manufacturers are constantly launching car models by system is introduced. Implementation details of the XM advancing and adopting more effective design and function module, such as control commands and device manufacturing techniques in order to meet the communication protocol of the XM tuner, the state increasingly picky taste of hypercritical automobile transition matrix layer and the application layer are also consumers. The quality of digital car audio system presented in this work. configuration has a considerable decisive impact on the Index Terms—XM radio, digital car audio system, purchasing selection of automobile consumers. The embedded system, ITRON, communication protocol, state improvement of function and quality of digital car audio transition matrix. systems is becoming ever more important for both automobile manufacturers and automobile consumers. This paper focuses on the design and implementation I. INTRODUCTION process of a function module named the XM radio module in a real development project of a digital car With the rapid development of the automobile audio system. The digital car audio is a sub-system of an manufacturing industry and rapid growth of the travel on board electronic control system, which operates within demand of consumers, the global automobile sales is a software environment provided by the embedded real- magnifying year by year. The strong demand in the time operating system compliant with industry standard automobile consumer market has prompted the ITRON [2,3]. General development techniques and the maturation and development of a series of other related application status quo of car audio systems are displayed industries, the digital car audio manufacturing industry is in this work. a typical example of these industries. As the extension of automobile manufacturing industry into electronic II. XM BROADCAST RADIO SERVICE © 2012 ACADEMY PUBLISHER doi:10.4304/jsw.7.9.1981-1992 1982 JOURNAL OF SOFTWARE, VOL. 7, NO. 9, SEPTEMBER 2012 XM is a SDARS (Satellite Digital Audio Radio Touch Panel Service) [4,5] broadcast radio service operated by the US Display company SiriusXM in North American regions including XM Radio Service the USA and Canada of. SDARS is a branch of digital Video-Audio Speaker Satellite audio broadcasting [6] services which incorporates Microcontroller multiple communication satellites for radio program broadcasting. IEBUS XM radio program signal is delivered by five of the Main DSP XM Tuner nine in-orbit satellites of the SiriusXM Company. The Microcontroller I2S radio program signal is transmitted to and then broadcast from these satellites to the ground listening devices. The Key Control Panel working band of XM radio service rests on the 2.3GHz S band, with frequency ranging from 2320MHz to 2345MHz. Figure 1. Block diagram of XM car audio system hardware XM service was launched on September 25, 2001 in related to broadcast radio functionality. the USA, providing high quality broadcast radio service that surpasses existing radio services like FM and AM on the other hand, it has several special requirements for both in sound quality and geographic coverage. In order both software and hardware configuration of the digital to maintain signal strength, in areas where signals may car audio system. The detailed hardware configuration weaken greatly, like places in the vicinity of high rise can be seen in Figure 1. buildings in downtowns and under-ground car parks A. Hardware Requirements where satellite signal might be blocked, ground receivers are installed to rebroadcast signal to guarantee constant The hardware requirements of XM broadcast radio and full coverage for subscriber usage. functionality can be separated into two classes. The first Since the XM radio service adopts a business model class includes hardware shared among many different base on paid subscription, various kinds of programs with system functions, like microcontrollers on which the rich content and premium sound quality are provided to operating systems run, chips that can process and adjust the users,. At present, there are over 180 stations whose audio signals, speakers that play processed audio signals types span of music, news & talk, sports, and traffic & input from the main microcontroller, display screen that whether available in the XM radio service, some displays system states, key control panels, and touch automobile owner can listen to the XM radio service with panel display. The second class includes special hardware the eight-digit identity number called Radio ID assigned specifically required by the XM broadcast radio to each on board XM tuner device for three month trial functionality, which includes external devices that can period usually provided by the automobile manufacturer. receive broadcast radio signal from the satellites and the By the end of the year 2010, the number of subscribers to data communication bus that establishes data exchange the XM radio service operated the SiriusXM company on the connection between the microcontroller and the has exceeded 20 million to 20.19 million, showing strong external device. In the development project of the digital market demand for satellite broadcast radio service, the car audio system, an XM satellite broadcast radio signal sales of digital car audio systems with preinstalled XM receiver called XM tuner is adopted to receive radio radio listening devices and corresponding software program signal from the satellites, and a data solution will benefit from this process of market demand communication bus named IEBUS is used to connect the growth dramatically. XM tuner to the microcontroller in the head unit of the digital car audio system. During the design phase of the car audio system III. REQUIREMENT ANALYSIS OF THE IMPLEMENTATION product, taking into account the conservation of OF XM BROADCAST RADIO FUNCTION manufacturing cost and differences of device control and In general, the objective of the development project is data processing demands for the whole car audio system to establish a digital car audio system that consists of in the actual environment, two microcontrollers with microcontrollers, display screen, operation panel of keys, different processing capabilities are adopted. multiple external devices and speakers. These For the special demands for user interface drawing on components provide users with a series of complete car the LCD screen and decoding processing of video media audio system functionalities that include signal content, a video audio microcontroller customized for processing, system state display, user input acquisition, graphics performance optimization is adopted. playback of media content in external connected devices The other microcontroller, namely the main and sound output to the users. XM broadcast radio is one microcontroller is responsible for power management, of the functionalities that needs to implement in the car audio signal output to DSP chips for sound output, audio development project. The integration of XM radio detection of key press on the control panel, and data may be discussed from two perspectives. On one hand, exchange with several external devices via different kinds the XM radio module relies on the common infrastructure of data communication buses. shared among other digital car audio system function The two microcontrollers are connected by 32-bit data modules like FM/AM radio, Bluetooth audio and so on, communication bus named CSI (Configurable System © 2012 ACADEMY PUBLISHER JOURNAL OF SOFTWARE, VOL. 7, NO. 9, SEPTEMBER 2012 1983 Interconnect). Via the CSI bus, the two microcontrollers IV. ARCHITECTURE OF DEVELOPMENT FOR XM can exchange data with each other according tocertain BROADCAST RADIO FUNCTION inter-microcontroller communication mechanism. The implementation of XM function is divided onto two microcontrollers.

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